Opportunistic infections may occur in immunocompromised or normal hosts and this possibility should be considered when there is failure to respond to initial antibiotic therapy. If appropriate: HIV antibodies, assessment of immune function.

See also Infection (increased susceptibility)

Immunocompromised host

The common pathogens are the most likely cause of pneumonia, but unusual pathogens should be considered early, especially when the illness is severe or when the initial response to therapy is unsatisfactory. Investigation may include: MCS sputum, MCS Bronchoalveolar lavage (bronchial brush, wash; bronchoalveolar lavage), Fine needle aspiration biopsy or endoscopic lung biopsy - microscopy, culture (including mycobacterial and fungal). Open lung biopsy may be required.